linux-kernel - [PATCH 1/4] RISC-V: Do not allocate memblock while iterating reserved memblocks

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Message-Id: <20210107092652.3438696-2-atish.patra@wdc.com>
Date:   Thu,  7 Jan 2021 01:26:49 -0800
From:   Atish Patra <atish.patra@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atish.patra@....com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anup Patel <anup.patel@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        linux-riscv@...ts.infradead.org, Mike Rapoport <rppt@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Nick Kossifidis <mick@....forth.gr>
Subject: [PATCH 1/4] RISC-V: Do not allocate memblock while iterating reserved memblocks

Currently, resource tree allocates memory blocks while iterating on the
list. It leads to following kernel warning because memblock allocation
also invokes memory block reservation API.

[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: CPU: 0 PID: 0 at kernel/resource.c:795
__insert_resource+0x8e/0xd0
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
5.10.0-00022-ge20097fb37e2-dirty #549
[    0.000000] epc: c00125c2 ra : c001262c sp : c1c01f50
[    0.000000]  gp : c1d456e0 tp : c1c0a980 t0 : ffffcf20
[    0.000000]  t1 : 00000000 t2 : 00000000 s0 : c1c01f60
[    0.000000]  s1 : ffffcf00 a0 : ffffff00 a1 : c1c0c0c4
[    0.000000]  a2 : 80c12b15 a3 : 80402000 a4 : 80402000
[    0.000000]  a5 : c1c0c0c4 a6 : 80c12b15 a7 : f5faf600
[    0.000000]  s2 : c1c0c0c4 s3 : c1c0e000 s4 : c1009a80
[    0.000000]  s5 : c1c0c000 s6 : c1d48000 s7 : c1613b4c
[    0.000000]  s8 : 00000fff s9 : 80000200 s10: c1613b40
[    0.000000]  s11: 00000000 t3 : c1d4a000 t4 : ffffffff

This is also unnecessary as we can pre-compute the total memblocks required
for each memory region and allocate it before the loop. It save precious
boot time not going through memblock allocation code every time.

Fixes: 00ab027a3b82 ("RISC-V: Add kernel image sections to the resource tree")

Signed-off-by: Atish Patra <atish.patra@....com>
---
 arch/riscv/kernel/setup.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 1d85e9bf783c..3fa3f26dde85 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -127,7 +127,9 @@ static void __init init_resources(void)
 {
 	struct memblock_region *region = NULL;
 	struct resource *res = NULL;
-	int ret = 0;
+	struct resource *mem_res = NULL;
+	size_t mem_res_sz = 0;
+	int ret = 0, i = 0;
 
 	code_res.start = __pa_symbol(_text);
 	code_res.end = __pa_symbol(_etext) - 1;
@@ -145,16 +147,17 @@ static void __init init_resources(void)
 	bss_res.end = __pa_symbol(__bss_stop) - 1;
 	bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
+	mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) * sizeof(*mem_res);
+	mem_res = memblock_alloc(mem_res_sz, SMP_CACHE_BYTES);
+	if (!mem_res)
+		panic("%s: Failed to allocate %zu bytes\n", __func__, mem_res_sz);
 	/*
 	 * Start by adding the reserved regions, if they overlap
 	 * with /memory regions, insert_resource later on will take
 	 * care of it.
 	 */
 	for_each_reserved_mem_region(region) {
-		res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
-		if (!res)
-			panic("%s: Failed to allocate %zu bytes\n", __func__,
-			      sizeof(struct resource));
+		res = &mem_res[i++];
 
 		res->name = "Reserved";
 		res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
@@ -171,8 +174,10 @@ static void __init init_resources(void)
 		 * Ignore any other reserved regions within
 		 * system memory.
 		 */
-		if (memblock_is_memory(res->start))
+		if (memblock_is_memory(res->start)) {
+			memblock_free((phys_addr_t) res, sizeof(struct resource));
 			continue;
+		}
 
 		ret = add_resource(&iomem_resource, res);
 		if (ret < 0)
@@ -181,10 +186,7 @@ static void __init init_resources(void)
 
 	/* Add /memory regions to the resource tree */
 	for_each_mem_region(region) {
-		res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
-		if (!res)
-			panic("%s: Failed to allocate %zu bytes\n", __func__,
-			      sizeof(struct resource));
+		res = &mem_res[i++];
 
 		if (unlikely(memblock_is_nomap(region))) {
 			res->name = "Reserved";
@@ -205,9 +207,9 @@ static void __init init_resources(void)
 	return;
 
  error:
-	memblock_free((phys_addr_t) res, sizeof(struct resource));
 	/* Better an empty resource tree than an inconsistent one */
 	release_child_resources(&iomem_resource);
+	memblock_free((phys_addr_t) mem_res, mem_res_sz);
 }
 
 
-- 
2.25.1